The present invention relates to a method for detecting a position of a micro-mark on a substrate by using an electron beam, and more especially to a method which can be effectively used when a pattern for a semiconductor integrated circuit such as an IC (integrated circuit) or LSI (large scale integrated circuit) is formed on a semiconductor substrate by an electron beam exposing apparatus which emits an electron beam.
The detection of the position of a micro-mark is conventionally carried out during an electron beam exposure process of an electron beam sensitive resist deposited on a wafer for forming a pattern when the semiconductor integrated circuit is manufactured.
In a process of forming a pattern: before the process of forming a pattern, a wafer is positioned on a holder, the holder is mounted on a stage and the stage is fixed in a main chamber. When the stage is fixed in the main chamber, positioning error of the wafer is caused by errors of the shapes of the wafer and the holder or by errors caused by mechanical inaccuracy of the apparatus for introducing the holder into the main chamber. Therefore, a magnification factor or a reduction factor of the pattern and the position of a focus point of the electron beam is adjusted by detecting the position of a micro-mark formed on the wafer.
Conventionally, this detection of the micro-mark was carried out in the following manner. Before the process of forming a pattern, the electron beam scans with a relatively large pitch the predetermined region where the micro-mark is included. When the electron beam passes over the micro-mark, the variation of the secondary electrons is detected by a secondary electron multiplier, and this variation forms a corresponding pattern on a display apparatus which is externally provided. Then, an operator manually positions the stage, by observing the position of the micro-mark on a display screen or panel so as to place the micro-mark image on the display screen or panel at the center of the display screen, preliminary to the succeeding operations for precisely detecting the position of the micro-mark and then compensating the positioning errors.
As mentioned above, in the conventional method for detecting a micro-mark, a display device is used and the operation is performed by an operator. If the whole scanning area is scanned by an electron beam with a minute pitch to precisely detect the position of the micro-mark which assures the precise position compensation, much more time will be required to finish the scanning operation because a slow scan must be carried out with a sharp electron beam over the whole scanning area to obtain the necessary precision. Therefore, much time is required for detecting the position of the micro-mark in the conventional method.